Smalltalk Syntax Cheat Sheet

This page extracted from the "Smalltalk/X Programmers guide - Smalltalk/X Cheat Sheet"

A short, one page summary of what beginners need to know about Smalltalk/X syntax

Syntax

Comments

Regular comment	" this is a comment "	any text between double quotes
EOL-Comment	"/ this is an End-of-Line comment	text from quote-slash to line end
Token-Comment	"<<END a multiline token-comment up to a line starting with 'END' more commented stuff here ... comment ends here END	text up to line beginning with token after ">>"

Literal Constants

Integers	12345 -12345
Large integers	1234567890123456789012345…	arbitrary number of digits
Integers with radix (Smalltalk style)	16rAFFE, 2r010101, 8r0777, 3r012012, 16r-AFFE, 2r-010101	prepend the radix (base) any radix possible
Integers with radix (C style)	0xFEED -0xBEAF 0b11011,-0b1100	C/Java/JavaScript style: prepend radix indicator ('x', 'b', 'o') One of hex, binary and octal
Floats (IEEE double; roughly 17 decimals)	12.456 1.234e17 -6.9 -6e-10 Float pi Float e	called "Float", but actually hold double precision
Short floats (IEEE single; roughly 8 decimals)	1.234f17 -6f-10
Long floats (IEEE quad; roughly 20 decimals)	1.234q17 -6q-10	actual precision depends on the underlying CPU (on x86/x86_64: only 80bit)
High prec. floats; roughly 60 decimals	1.234Q17 -6Q-10	computed in software; therefore slower; this is not yet officially released.
Fractions	(1/3) (17/2)
Characters	$a Character space Character nl Also: "null", "tab", "return", "bell"...
Strings	'hello'	traditionally, Smalltalk does not support any escape sequence inside
Strings (C Style)	c'hello\nworld'	supports the common escape sequences, such as "\n", "\t", "\xHH"
Symbols	#'hello' #foo (without quotes, if only alphaNumeric characters)
Arrays	#( el1 el2 ... elN ) each element a literal constant
Byte Arrays	#[ b1 b2 ... bN ] each byte-element an integer constant in 0..255
Special Number Arrays	#XX( v1 v2 ... vN ) XX: is one of  'u8', 's8', 'u16', 's16', 'u32', 's32', 'u64', 's64', 'f32', 'f64'  and each element being an integer or float constant
Immediate Inline Objects	#{ foo: fooValue . bar: barValue } fooValue and barValue: constant

Lambda Blocks (Closures)

Without argument	[ expr1 . expr2 ... exprN ] when evaluated, the value is the value  from the last expression, exprN
One argument	expr1 . expr2 ... exprN ]
Multiple arguments	expr1 . expr2 ... exprN ]

Expressions

the receiver expression is evaluated, then multiple messages (separated by ";") are sent to this receiver.

Unary Expression (without argument)	receiver messageName receiver is itself either a constant, a lambda-block, a unary expression or a parenthesized expression
Keyword Expression: (1 arg)	receiver messageNamePart:argExpression whitespace between the colon and the argExpression is optional.
Keyword Expression: (any number of args)	receiver     messageNamePart1:argExpression1     messageNamePart2:argExpression2     ...     messageNamePartN:argExpressionN
Binary Expression	receiver binOP arg with binOP being any combination of special characters: * , + , - , % , & , / , \ , | , = , < , > , ? and , I.e. "foo ==> 123" is the binary message "==>" sent to foo with 123 as argument. And "foo ? 123" is the binary message "?" sent to foo with 123 as argument.
Cascade Expression (sending multiple messages to the same receiver)	receiver message1 ; message2 ; ... messageN
Parentheses for grouping	( any expression )
Assignment	variable := expression can be used as expression.
Computed Array (Brace Construct)	{ expr1 . expr2 . ... . exprN } instantiates a new Array object with elements from the expressions.
Computed Inline Objects	{ foo: fooExpr . bar: barExpr } fooExpr and barExpr: expressions

Remaining Syntax

Local variables (in block or method)	var1 var2 ... varN | variable declarations must be at the beginning, before any expression.
Separating multiple expressions (sequence)	expr1 . expr2 . ... exprN expressions (statements) are separated by fullstop (period) characters. The last expression may or may not be followed by a fullstop; if there is one, this is treated like a followup empty statement.
Return from method	^ expression returns from the enclosing method (also if inside a block-closure)

Wellknown (Common) Messages

Conditional Execution	boolExpr1 ifTrue:[ ... ] ifFalse:[ ... ] variations without true-part, without false part and with the order reversed are available.
While-Loop	[ boolExpr1 ] whileTrue:[ ... ] notice the receiver being a block. A whileFalse variant is also available.
For-Loop	... ] evaluates the lambda for each value in start..stop.
Enumerating Collections	... ] evaluates the lambda for each element in the collection.
Evaluating a Lambda Block   without arguments:   with arguments:	aBlock value aBlock value:expr1 ... value:exprN the number of arguments must match the number expected by the lambda (although varArg lambdas are also available)

Wellknown Globals

Logging and Messaging

Transcript - console window Stdout - standard output Stderr - standard error Stdin - standard input Logger - redefinable logger (defaults to standard error)

Most Wellknown Classes

Collections	Array (fixed size array) OrderedCollection, List (variable size) SortedCollection Set, Bag (unordered) Dictionary (mapped collections) BinaryTree, AVLTree SharedQueue (shared, synchronized) many more...
Process Handling	Process (lightweight thread) OSProcess (heavyweight OS process) Semaphore, RecursionLock (synchronization) Monitor, BoltLock Delay
Files & Streams	Filename (file naming, directory access, mime type) Stream (basic stream framework) ReadStream, WriteStream, EncodedStream ExternalStream, FileStream, Socket (OS streams)
Low Level Access	OperatingSystem (OS API calls) Smalltalk(startup, shutdown and globals) ObjectMemory (VM access)

---

Copyright © 2014-2024 eXept Software AG